linux-kernel - Re: [PATCH] PCI: qcom-ep: Do not enable resources during probe()

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Message-ID: <20240813170247.GA26796@thinkpad>
Date: Tue, 13 Aug 2024 22:32:47 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org,
	bhelgaas@...gle.com, linux-arm-msm@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: qcom-ep: Do not enable resources during probe()

On Sat, Jul 27, 2024 at 01:32:40PM +0300, Dmitry Baryshkov wrote:
> On Sat, Jul 27, 2024 at 02:36:04PM GMT, Manivannan Sadhasivam wrote:
> > Starting from commit 869bc5253406 ("PCI: dwc: ep: Fix DBI access failure
> > for drivers requiring refclk from host"), all the hardware register access
> > (like DBI) were moved to dw_pcie_ep_init_registers() which gets called only
> > in qcom_pcie_perst_deassert() i.e., only after the endpoint received refclk
> > from host.
> > 
> > So there is no need to enable the endpoint resources (like clk, regulators,
> > PHY) during probe(). Hence, remove the call to qcom_pcie_enable_resources()
> > helper from probe(). This was added earlier because dw_pcie_ep_init() was
> > doing DBI access, which is not done now.
> 
> ... moreover his makes PCIe EP fail on some of the platforms as powering
> on PHY requires refclk from the RC side, which is not enabled at the
> probe time.
> 

Yeah. I hope Bjorn/Krzysztof could add this to the commit message while
applying.

> Tested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> 

Thanks!

- Mani

> > While at it, let's also call dw_pcie_ep_deinit() in err path to deinit the
> > EP controller in the case of failure.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom-ep.c | 14 ++++----------
> >  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> -- 
> With best wishes
> Dmitry

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